1. Field of the Invention
This invention relates to a drive transmission device, a lens unit using the drive transmission device, an optical apparatus that includes an imaging unit to which the lens unit is detachably mounted, and an optical-apparatus driving unit that is mounted to the lens unit using the drive transmission device.
2. Description of the Related Art
FIG. 9 shows the structure of a manually-operated part and an electrically-operated system of a conventional optical apparatus, such as that used for television shooting.
An operating ring 103 is rotatably disposed on the outer periphery of an apparatus body 101. An optical adjusting means, such as a movable lens group, not shown, that is disposed inside the apparatus body 101 can be driven by manual operation of the operating ring 103 or by electric operation from a drive unit mounted in the apparatus body 101.
A motor 105 and a control circuit used to electrically drive the operating ring 103 are housed in the drive unit. The motor 105 can be activated by operating an electric operation switch, or the like, that is disposed on the outer surface of the drive unit, and the optical adjusting means can be driven through the operating ring 103.
In the optical apparatus capable of manually and electrically driving the movable lens group, switching between manual drive and electric drive is carried out in most cases by manually operating a clutch mechanism provided with a switching lever.
In this clutch mechanism, an idler gear 123 slidable in the axial direction of a shaft 124 by the operation of the switching lever, not shown, is provided between an operating gear 104 formed on the operating ring 103 and an output gear 122 of the motor 105.
When electrically driven, the idler gear 123 is slid by the manual operation of the switching lever to a position where the idler gear 123 is engaged with the operating gear 104 and with the output gear 122, thereby transmitting the driving force of the motor 105 to the operating ring 103 through the idler gear 123.
When manually driven, the idler gear 123 is slid by the manual operation of the switching lever to a position where the idler gear 123 is disengaged from the output gear 122.
The switching between manual drive and electric drive is conventionally carried out such that a driving-force transmission path from the motor 105 to the operating ring 103 is turned on or off by manually operating the clutch mechanism, as described above.
However, in the optical apparatus in which the transmission path of motor power is turned on or off by operating the switching lever so as to achieve the switching between manual drive and electric drive as described above, the switching lever must be operated whenever the switching therebetween is carried out. Therefore, there is a problem in that operations become complex, and thus quick switching between manual drive and electric drive is made difficult.
Additionally, if the idler gear 123 and the output gear 122 are different in phase from each other when switched from manual drive to electric drive, the idler gear 123 is first pressed against the side surface of the output gear 122 by the urging force of the spring 125, and is caught there. Thereafter, when the output gear 122 begins to be driven by the motor 105, and the phase of the output gear 122 coincides with that of the idler gear 123, the gears mesh with each other, and the idler gear 123 is moved to a contact position with a stopper 126 by the urging force of the spring 125. As a result, switching to a proper electric-drive state is completed.
However, a problem resides in that an impulse sound occurs at this time because the idler gear 123 collides with the stopper 126 owing to the urging force of the spring 125.
Further, in actual shooting, there is a case in which, while being electrically driven, a cameraman attempts to forcibly stop the electric drive through the manual operation of the operating ring 103, or attempts to perform the manual operation in a direction opposite to the electric-drive direction, or attempts to increase or decrease the electric-drive speed.
However, a problem resides in that the aforementioned clutch mechanism has difficulty in the manual operation while being electrically driven.
As consideration, use can be made of an electromagnetic clutch in which the electricity supply to a coil is turned on or off so as to turn on or off the transmission path of the motor power, which is different from the clutch mechanism in which the switching is carried out through the lever operation.
FIG. 8 shows the inner structure of the electromagnetic clutch. (a) of FIG. 8 shows the electromagnetic clutch in which the electricity supply to a coil 217 is in an off-state. At this time, an armature 215 connected to the operating ring 103 through a gear train, not shown, is drawn by the urging force of a leaf spring 222 in a direction opposite to a rotor 214 to which a driving force is input from a motor not shown so that the frictional surface 216 of the rotor 214 and the frictional surface 216 of the armature 215 do not come in contact with each other.
(b) of FIG. 8 shows the electromagnetic clutch in which the electricity supply to the coil 217 is in an on-state. At this time, a magnetic circuit is produced inside the electromagnetic clutch, and the armature 215 is drawn to the rotor 214 against the urging force of the leaf spring 222 and is brought into pressed contact with the rotor 214. Thereafter, engagement torque is generated in the electromagnetic clutch by the frictional force of the frictional surface 216, and the driving force of the motor can be transmitted to the operating ring 103.
However, if the electromagnetic clutch constructed as shown in FIG. 8 is used, the armature 215 moves in response to the switching between the ON and the OFF of the electricity supply to the coil 217 and collides with the rotor 214 or with the striking surface of the output shaft, and therefore a noise occurs.
Additionally, an electromagnetic force (i.e., coil voltage) that prevails against the urging force of the spring 222 is required in order for the armature 215 to come in contact with the rotor 214 by attraction. Therefore, delay arises during the period from the start of a command signal for performing the electric drive to the occurrence of the engagement torque resulting from the attractive contact of the armature 215 with the rotor 214.
Additionally, the coil voltage required to cause the armature 215 to come in contact with the rotor 214 by attraction is inconstant because, for example, of the individual differences of the electromagnetic clutch.
It is therefore an object of the present invention to provide a drive transmission device capable of preventing a sound from occurring when switched between the ON and OFF of the electricity supply, and capable of eliminating delay caused during the period from the beginning of the electricity supply to the engagement between an input member and an output member.
It is another object of the present invention to provide an optical apparatus or an optical-apparatus driving unit capable of easily, promptly, and quietly performing the switching between manual drive and electric drive by use of the aforementioned drive transmission device, and capable of smoothly performing the manual drive while being electrically driven.
In order to achieve the objects, according to the present invention, a drive transmission device for transmitting the drive of an actuator to a driven member comprises an input member which is driven by the actuator, an output member for transmitting the drive of the input member and driving the driven member, and a state switching unit for performing switching between a first state to transmit drive and a second state so as not to transmit drive in the input member and the output member, in which the input member and the output member are in contact with each other when the state switching unit is in the first state and in the second state.
Further, according to the present invention, an optical apparatus includes a drive transmission device for transmitting drive so as to manually drive an optical member by manually operating a manual-drive member and so as to electrically drive the optical member by transmitting electric drive from an actuator to the manual-drive member. The optical apparatus comprises an optical unit which movably supports the optical member driven by the manual-drive member, an input member driven by the actuator, an output member for transmitting the drive of the input member and driving the manual-drive member, and a state switching unit for performing switching between a first state to transmit drive and a second state so as not to transmit drive in the input member and the output member, in which the input member and the output member are in contact with each other when the state switching unit is in the first state and in the second state.
Further, according to the present invention, an optical apparatus includes a drive transmission device for transmitting drive so as to manually drive an optical member by manually operating a manual-drive member and so as to electrically drive the optical member by transmitting electric drive from an actuator to the manual-drive member. The optical apparatus comprises an optical unit which movably supports the optical member driven by the manual-drive member, an input member driven by the actuator, an output member for transmitting the drive of the input member and driving the manual-drive member, a state switching unit for performing switching between a first state to transmit drive and a second state so as not to transmit drive in the input member and the output member, a command unit for commanding the optical member to be electrically driven, which outputs command information in accordance with operation of a command operating member to the actuator, and a controller for controlling the state switching unit in accordance with the command information from the command unit, in which the input member and the output member are in contact with each other when the state switching unit is in the first state and in the second state.
Further, according to the present invention, an optical apparatus includes a drive transmission device for transmitting drive so as to manually drive an optical member by manually operating a manual-drive member and so as to electrically drive the optical member by transmitting electric drive from an actuator to the manual-drive member. The optical apparatus comprises an optical unit that movably supports the optical member driven by the manual-drive member, an imaging device to which the optical unit is detachably mounted and which has an image pickup device for picking up a subject image from the optical unit, an input member driven by the actuator, an output member for transmitting the drive of the input member and driving the manual-drive member, a state switching unit for performing switching between a first state to transmit drive and a second state so as not to transmit drive in the input member and the output member, a command unit for commanding the optical member to be electrically driven, which outputs command information in accordance with operation of a command operating member to the actuator, and a controller for controlling the state switching unit in accordance with the command information from the command unit, in which the input member and the output member are in contact with each other when the state switching unit is in the first state and in the second state.
Further, according to the present invention, an optical-apparatus driving unit mounted or connected to a body of an optical apparatus including an optical member includes a drive transmission device in which the optical member can be manually operated by manual operation input to a manual-drive member and in which the optical member can be electrically driven by transmitting electric drive from an actuator to the manual-drive member. The optical-apparatus driving unit comprises an input member driven by the actuator; an output member for transmitting the drive of the input member and driving the manual-drive member; a state switching unit for performing switching between a first state to transmit drive and a second state so as not to transmit drive in the input member and the output member; a command unit for commanding the optical member to be electrically driven, which outputs command information in accordance with operation of a command operating member to the actuator; and a controller for controlling the state switching unit in accordance with the command information from the command unit; in which the input member and the output member are in contact with each other when the state switching unit is in the first state and in the second state. Further objects and structures of the present invention will become apparent from description of embodiments provided later.